Method for the disposal of combustible and dilute aqueous wastes

ABSTRACT

A METHOD FOR THE DISPOSAL OF COMBUSTIBLE AND DILUTE AQUEOUS WASTES IN WHICH POTABLE WATER AND USEFUL POWER ARE KPRODUCED. COMBUSTIBLE WASTE, TOGETHER IF NECESSARY WITH CONVENTIONAL FUEL, IS BURNED IN A FLUIDIZED-BED STEAM GENERATOR, THE STEAM THUS PRODUCED IS USED TO EVAPORATE DILUTE AQUEOUS WASTES IN THE FIRST STAGE OF A TWO-STAGE FLUIDIZED-BED EVAPORATOR; THE STREAM INTHE FIRST STAGE IS USED TOEVAPORATE DILUTE AQUEOUS WASTES IN THE SECOND STAGE OF THE TWO-STAGE FLUIDIZED-BED STEAM GENERATOR; TNE STEAM PRODUCED IN THE SECOND STAGE IS USED TO GENERATE POWER; AND THE SPENT STEAM FROM THE FIRST AND SECOND FLUIDIZED-BED EVAPORATORS IS CONDENSED AS POTABLE WATER.

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Filed June 5.

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AND DILUTE AQUEOUS WASTES www. vlmnunlnw Ni QmNES E. S. GRIMMETT TAL METHOD Fon THE DISPOSAL oF COMBUSTIBLE ,www m Aug. 6, 1974 United States Patent O 3,827,946 METHOD FOR THE DISPOSAL OF COMBUSTIBLE AND DILUTE AQUEOUS WASTES Earl S. Grimmett and Philip E. Lamont, Idaho Falls, Idaho, assignors to the United States of America as represented by the United States Atomic Energy Commission Filed June S, 1972, Ser. No. 259,797 Int. Cl. B01d 3/00 U.S. Cl. 203- 2 Claims ABSTRACT OF THE DISCLOSURE A method for the disposal of combustible and dilute aqueous wastes in which potable water and useful power are produced. Combustible waste, together if necessary with conventional fuel, is burned in a iiuidized-bed steam generator; the steam thus produced is used to evaporate dilute aqueous wastes in the first stage of a two-stage iiuidized-bed evaporator; the steam in the first stage is used to evaporate dilute aqueous Wastes in the second stage of the two-stage uidized-bed steam generator; the steam produced in the second stage is used to generate power; and the spent steam from the iirst and second uidized-bed evaporators is condensed as potable water.

CONTRACT UAL ORIGIN OF THE INVENTION The invention described herein was made in the course of, or under, a contract with the United States Atomic Energy Commission.

BACKGROUND OF THE INVENTION This invention relates to a waste disposal process. In more detail, the invention relates to a waste management process for disposing of combustible and dilute aqueous wastes wherein potable water and useful power are produced. In other words, the invention relates to a process for producing useful power and potable water from cornbustible and dilute aqueous wastes.

The multitudinous problems arising from the seemingly infinite quantity of waste materials produced in our populous and highly industrialized society have resulted in a multitude of proposed solutions. Most proposed procedures for waste disposal treat a single type of waste without attempting to consider how all or most industrial and municipal wastes could be treated according to a unified scheme. All proposed procedures have one thing in common; they are expensive. In other areas it is common to reduce expense by utilizing by-products which may be vastly different from the primary product of the process. There is no reason why waste management should be different and, of course, by-product utilization of, for example, sludges as fertilizer is common. According to the present invention, waste management techniques that have recently been developed for the management of radioactive wastes are utilized in a process for handling combustible and dilute aqueous industrial and municipal wastes wherein the cost of Waste disposal is reduced by the value of potable water and useful power produced in the process.

SUMMARY OF THE INVENTION Accordingly to the present invention, uidized-bed techniques are employed to dispose of combustible waste materials and dilute aqueous wastes and simultaneously produce useful power and potable water.

Combustible trash plus any necessary conventional fuel is burned in a uidized-bed burner which is used to generate steam. The steam thus produced is used to evaporate dilute aqueous wastes in the first stage of a iiuidized-bed 3,827,946 Patented Aug. 6, 1974 ICC BRIEF DESCRIPTION OF' THE DRAWING The invention will next be described in connection with the accompanying drawing wherein the single figure is a flow sheet of a waste disposal process wherein electrical power and potable water are produced.

SPECIFIC EMBODIMENT OF THE INVENTION As shown in the drawing, a bed 10 of sand particles or some other inert material in fluidized-bed steam generator 11 is fluidized with air introduced into the bed through line 12. Combustible trash, introduced into steam generator through line 13, and a conventional fuel such as kerosene, introduced through line 14, are burned in the iluidized-bed steam generator to boil water contained within coil 15 which is disposed within iluidized bed 10. Off-gases leave the steam generator through line 16 and are subjected to conventional scrubbing practices in gas scrubber 17 before release to the atmosphere.

Steam at a temperature of l000 F. and pressure of 2400 p.s.i.a. formed in coil 15 are employed to heat and tiuidize a bed 18 of sand particles or some other inert material contained within the first stage 19 of a uidizedbed evaporator, about 10% of the steam from coil 15 being directed to the bottom of first stage 19 of the iiuidized-bed evaporator through line 20 to uidize ythe bed 18 of sand particles and the remainder of the steam from coil 15 being directed through line 21 to coil 22 immersed within iluidized bed 18 to heat the fluidi'zed bed 10. From coil 22 the condensed steam (hot water) is directed to preheater 23 through line 24 where it gives up its heat to dilute aqueous wastes such as municipal sewage introduced thereinto through line 25, the aqueous wastes then being sprayed into the first stage of the fluidized-bed evaporator through line 26 and the cooled water from preheater 23 being returned to coil 15 through line 27. Makeup water is obtained from the fresh water produced in the system so that the iiuidizing steam for evaporator 19 circulates within the system.

About 10% of thesteam produced in the first stage 19 of the fiuidized-bed evaporator at a temperature of 550 F. and pressure of 1055 p.s.i.a. is conducted through line 29 to the bottom of second stage 30 of uidized-bed evap orator to fluidize a bed 31 of sand particles or another inert material contained therein, the remainder of l,the steam produced in the lirst stage being conducted through line 32 to coil 33 disposed in uidized bed 31. Dilut aqueous wastes are fed into preheater 34 from line'u25 where they ilow countercurrent to hot water coming from coil 33 in the second-stage iuidized-bed evaporator through line 35. Steam produced in second-stage fiuidizedbed evaporator 30 at a temperature of 450 F. and pre' sure of 425 p.s.i.a. is conducted to turbine generator through line 37 prior to being condensed in condenseil 38. The fresh water obtained from condenser 38 and prel heater 34 constitutes one of the useful products of Ihe process. In addition, combustible solids produced in both stages of uidized-bed evaporation may be fed to fl (i ized-bed steam generator 11 as indicated by dotted s1 tem and at the same time dispose of its burnable solidtrash.

.According to an alternative arrangement, the steam from uidized-bed steam generator 11 can be introduced into al back pressure turbine and then introduced into the headend of a multistage uidized-bed evaporator. By using this system, the advantage of generating high-pressure superheated steam is obtained. According to another a1- ternate, steam from the fluidized-bed steam generator 11 is passed through a turbine which generates both electrical and mechanical power. The mechanical power is used to operate the compressor used in a vapor compression cycle uidized-bed evaporator, and the electrical power can be a salable lay-product.

In order to make the electrical-generating capacity of this system match the quantity of sewage disposed of in this typical city, a system according to the present invention may be combined with an advanced sewage treatment plant proposed by others, wherein after secondary treatment a part of the Waste water is subjected to coagulation and sedimentation and another part is evaporated for purication. According to the present invention, the disclosedvtluidized-bed evaporation process is substituted for the conventional evaporation procedures contemplated in the prior suggestion.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: l

1. A method for the disposal of combustible and dilute aqueous wastes in which potable Water and useful power are produced comprising establishing and maintaining a lirst xfluidized bed of an inert material by passing air upwardly therethrough, boiling water in said lluidized bed -by burning combustible waste and conventional fuel therein, establishing and maintaining a second uidized bed of an inert material by passing a portion of the steam produced in the first uidized bed upwardly therethrough, introducing dilute aqueous wastes into said second uidized bed, evaporating the water from said dilute aqueous wastes by owing the remainder of the steam produced in the first iluidized bed through the second tluidized bed in indirect heat exchange with said dilute aqueous Wastes, preheating the dilute aqueous wastes prior to introducing them into the second iluidized bed with the hot water condensed in the second uidized bed from steam produced in the rst fluidized bed, returning the condensed water to the first uidized bed to be reboiled along with makeup water, establishing and maintaining a third lluidized bed of an inert material by passing a portion of the steam produced in the second fluidized bed upwardly therethrough, introducing dilute aqueous Wastes into said third lluidized bed, evaporating the Water from said dilute aqueous wastes by flowing the remainder of the steam produced in the second fluidized bed through the third iluidized bed in indirect heat exchange with said dilute aqueous wastes, preheating the dilute aqueous Wastes prior to their introduction into the third fluidized bed with the hot water condensed in the third fluidized bed from steam produced in the second uidized bed generating power from the steam developed in the third fluidized bed and recovering the spent steam from the second and third iiuidized beds as product water.

2. Method according to claim 1 wherein combustible solids obtained in both stages of the iiuidized bed evaporator are fed to the tiuidized-bed steam generator.

References Cited UNITED STATES PATENTS 3,306,236 2/1967 Campbell 110-8 R 3,491,822 1/1970 Ramaswami 159-Dig. 3 3,438,869 4/ 1969 Saavedra 203-10 3,323,575 6/1967 Greeneld 110-8 R 3,467,587 9/ 1969 Connell 203-Dig. 20 3,489,652 1/1970 Williamson 203-Dig. 20

NORMAN YUDKOFF, Primary Examiner F. SEVER, Assistant Examiner U.S. Cl. X.R.

--l08; 11G-8 R; 203-23, 25 

